Printer calibration module

ABSTRACT

An inkjet printer is disclosed that has a substrate support; a calibration module disposed adjacent to the substrate support and comprising a stage member; and a print assembly disposed across the substrate support, the print assembly comprising a printhead and a calibration imaging device positionable to face the stage member.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/880,129, filed May 21, 2021, which claims benefit of U.S. ProvisionalPatent Application Serial Nos. 62/855,675 filed May 31, 2019, and62/948,534 filed Dec. 16, 2019, each of which is entirely incorporatedby reference herein.

FIELD

Embodiments described herein generally relate to inkjet printers forindustrial applications. Specifically, embodiments of testing modulesfor industrial scale inkjet printers are described herein.

BACKGROUND

Large inkjet printers are often used to print patterns on largesubstrates with extreme precision. An example is the production ofdisplay screens. The various functional materials that produce anoperative display screen can be deposited on a glass substrate, oranother kind of substrate, by inkjet printing microscopic droplets onthe substrate and then solidifying the droplets into a functionalmaterial. The droplets can be as small as 10 μm in diameter, but must bedeposited in a way that forms a layer, or partial layer, of uniformthickness. Thus, the spacing of the droplet deposition must be extremelyprecise, with positional error of no more than about 10 μm in somecases. The print material is ejected from a printing assembly that hasone or more nozzles capable of creating the microscopic droplets, andthe precision requirements of such applications mean that the nozzlesmust dispense droplets very precisely and predictably.

In conventional printers, the print heads are tested by printing a testpattern on a substrate. A substrate similar to the substrate used tomake, for example, a display product is positioned in the printer, and atest pattern is printed on the substrate. The test pattern is evaluatedby photographing the printed test pattern and then performing imageprocessing to evaluate the accuracy of the printed pattern. This processtakes time to install and extract the substrate, and requires use of atest substrate, which can be expensive. There is a need for a moreefficient print head test module for industrial scale inkjet printers.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentdisclosure can be understood in detail, a more particular description ofthe disclosure, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlyexemplary embodiments and are therefore not to be considered limiting ofits scope, may admit to other equally effective embodiments.

FIG. 1A is an isometric view of a printer according to one embodiment.

FIG. 1B is a close-up view of a test module according to one embodiment.

FIG. 2 is a disassembled view of the test module of FIG. 1B.

FIG. 3 is a pre-operational view of the test module of FIG. 1B.

FIG. 4 is an operational view of the test module of FIG. 1B.

FIG. 5 is a partial cutaway view of a test cassette according to oneembodiment.

FIG. 6 is a detail view of a portion of the test cassette of FIG. 5 .

FIG. 7 is a side view of the test cassette of FIG. 5 .

FIG. 8 is a side view of the test module of FIG. 1B.

FIG. 9A is a top view of a substrate holder according to one embodiment.

FIG. 9B is a cross-sectional view of the substrate holder of FIG. 9A.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements and features of oneembodiment may be beneficially incorporated in other embodiments withoutfurther recitation.

DETAILED DESCRIPTION

FIG. 1A is an isometric view of a printer 100 according to oneembodiment. The printer 100 has a support surface 102 on which asubstrate is disposed for printing. The support surface 102 has aplurality of holes 104 through which gas is provided to form a gascushion to support the substrate. The support surface 102 has threesections. A first section 102A at a first end 103 of the support surface102 is a staging area for a substrate to be printed. A second section102B, in the middle of the support surface 102, is a print zone where asubstrate is positioned during printing. A third section 102C, at asecond end 104 of the support surface 102 opposite from the first end103, is also a staging area or support area for manipulating a substrateduring printing. The substrate is moved along the support surface 102from the first section 102A, through the second section 102B, to thethird section 102C to position various parts of the substrate forprinting.

The holes 104 in the second section 102B can be different from the holes104 in the first and third sections 102A and 102C. Some of the holes 104in the second section 102B can be used to remove gas from the gascushion to control substrate elevation above the support surface 102.Thus, the holes 104 in the second section 102B may have different pitch,size, or arrangement than the holes 104 in the first and third sections102A and 102C.

A print assembly 106 is disposed across and above the middle of thesupport surface 102. The print assembly 106 comprises two stands 108 anda beam 110 coupled to the two stands 108. The beam 110 extends acrossthe second section 102B of the support surface 102. A printhead assembly112 is coupled to the beam 110. The printhead assembly 112 includes acarriage 114 that coupled to the beam 110 and a printhead housing 116that couples to the carriage 114. The printhead housing 116 includes oneor more printheads (not visible in FIG. 1A) that dispense print materialonto a substrate positioned, at least in part, in the second section102B. The carriage 114 moves along the beam 110 to position theprinthead housing 116 along the support surface 102 in a firstdirection. The substrate is moved along the support surface 102 in asecond direction transverse to the first direction. In this way a targetlocation of the substrate can be positioned such that the printheads canbe brought into proximity for printing at the target location.

The support surface 102, print assembly 106, and test module 118 are allsupported on a massive base 115 that securely supports operation of theprinter with minimal vibration that could introduce errors into theprinting operation. The printhead assembly 112 can move to the end ofthe beam 110. At the near end of the beam 110, a test module 118 ispositioned adjacent to the support surface 102 next to one of the stands108. The printhead assembly 112 can move the printheads into proximityto the test module 118 to test print nozzle operation.

FIG. 1B is a close-up view of the test module 118. The test module 118has a mount 120 and a test cassette 122 that couples to the mount 120.The test module 118 is positioned on a linear actuator 124 that can movethe test module 118 along the second direction. The test cassette 122includes a testing substrate that can be repeatedly used to print testpatterns for evaluation. As further described below, the test module 118is scanned along the second direction while the printheads of theprinthead assembly dispense print material onto the testing substrate tosimulate production print conditions.

FIG. 2 is a disassembled view of the test module 118. The test cassette122 is shown decoupled from the mount 120. The test cassette 122 ispositioned on a tray 202 of the mount 120 for installation on the mount120. The tray 202 includes a latch 204 that securely holds the testcassette 122 upon installation and setting of the latch 204. The tray202 is moved into operating position by a tray actuator 206 locatedbelow a drive 208 that operates the test cassette 122 when installed onthe mount 120. The tray 202 rides on one or more slides 210 that extendfrom the drive 208 and allow linear motion of the tray 202 from anoperating position near the drive 208, so that the test cassette 122 cancouple to the drive 208, to a loading position away from the drive 208.The tray actuator 206 includes a rod 212 that couples the tray 202 tothe tray actuator 206 and moves the tray 202 along the slides 210.

The test cassette 122 includes a handle 214 to allow installation andremoval of a test cassette 122 from the mount 120. The test cassette 122includes a test substrate 216 that is maneuvered by co-operation of thetest cassette 122 and the drive 208, to a position at a top location ofthe test cassette 122 for access by the printheads. The drive 208 hastwo rotators 218 that rotate mandrels within the test cassette 122 tomanipulate the test substrate 216.

FIG. 3 is a pre-operational view of the test module 118. The testcassette 122 is disposed on the tray 202 and the latch 204 is set. Thetest substrate 216, positioned at the top location of the test cassette122, aligns with a vacuum extension 302 of the drive 208. The vacuumextension 302 extends from the drive 208 toward the test cassette 122from a top location of the drive 208. Structures of the test cassette122 not visible in this view lift the test substrate 216, enabling thevacuum extension 302 to extend below the test substrate 216 when thetest cassette 122 is coupled to the drive 208.

FIG. 4 is an operational view of the test module 118. The test cassette122 is moved into operating position near the drive 208. The vacuumextension 302 extends into the test cassette 122 and below the testsubstrate 216. The vacuum extension 302 includes a vacuum surface 402that applies a reduced pressure below the test substrate 216, ensuringthe test substrate 216 is very flat during a test print. If printmaterial is ejected toward a test substrate 216 that is not flat, thetest pattern can be distorted in unpredictable ways and the test mayfail. Prior to a test print, a vacuum source is coupled to the vacuumsurface 402 to reduce the pressure between the test substrate 216 andthe vacuum surface 402. The test substrate 216 is thus held securely onthe vacuum surface 402, with a clearance between the test substrate 216and the vacuum surface 402 of 5 μm or less. Deviation of the printsurface of the test substrate 216 from flatness, when secured to thevacuum surface 402, is less than about 5 μm.

The vacuum surface can be a surface of a porous body having sub-micronholes and passages therethrough to provide vacuum transmission throughthe porous body. In one case, the porous body is a porous carbon body,for example porous graphite, with 10-15% porosity, sub-micron pore size,and a vacuum surface with flatness of 2 microns. Porosity can be higheror lower. Higher porosity transmits vacuum to the vacuum surface moreeffectively. In the case of the 10-15% porosity embodiment describedabove, gas flow through the porous body is 0.2-0.3 L/min, for example0.25 L/min, at 0.09 MPa pressure difference through the porous body.

Higher porosity allows for more reliable chucking of a test substrateonto the vacuum surface without having to maintain very close proximityof the test substrate to the vacuum surface. Low porosity, and lowvacuum transmission, provides less chucking force, which can be madeeffective by providing higher tensioning of the test substrate tomaintain close proximity of the test substrate to the vacuum surface.

In some cases, the entire vacuum extension 302 can be a porous body,while in other cases the porous body can be a member of the vacuumextension 302. For example, the vacuum extension 302 can comprise aholder, and the porous body can be disposed in the holder. Using aholder can facilitate connection of a vacuum source to the vacuumextension 302. The holder can have two members that hold the porous bodyat either end of the long axis of the porous body. Alternately, theholder can be a rectangular member with a recess in a major surfacethereof where the porous body is inserted. The porous body can beembedded in the holder. The porous body can reside in an interior of theholder. For example, the holder can have a vacuum surface with aplurality of holes and an interior cavity that holds the porous body. Inembodiments featuring a holder, the holder can be made of any suitablematerial. Typically the holder is made of a structurally strong materialto support reliable connection to a vacuum source and reliable supportof a test substrate at the vacuum surface. Example materials includealuminum, ceramic, stainless steel, and the like.

Close proximity of the test substrate to the vacuum surface can also befacilitated by disposing a porous body in a holder such that the vacuumsurface of the porous body extends above the holder, for example by 0.1mm to 2 mm. Increasing width of the porous body can also help byreducing the curvature of the test substrate path above the vacuumsurface.

Here, the test substrate 216 has a long dimension and a short dimension.The long dimension is typically long enough for the test substrate 216to extend into the cassette and engage with a plurality of rollers andmandrels (not shown in this view). The short dimension is a dimensionselected to facilitate printing and evaluation of a test pattern on thetest substrate 216. The vacuum surface 402 has a long dimension similarto the short dimension of the test substrate 216. The vacuum surface 402has a short dimension selected to form a highly flat print surface forthe test print. The vacuum extension 302, in this configuration, extendsacross the top of the test cassette 122 under the test substrate 216 toa fork actuator 404. The fork actuator 404 is attached to a first sideof the test cassette 122 near the top thereof. A pair of forks 406extend from the fork actuator 404 toward the drive 208. The testsubstrate 216 extends across the forks 406. A first fork actuator 404extends along a first side 408 of the vacuum extension 302, while asecond fork actuator 404 extends along a second side 410 of the vacuumextension 302. The forks 406 and the fork actuator 404 constitute alifter. The fork actuator 404 is operable to extend upward, lifting theforks 406 and the test substrate 216 to facilitate inserting the vacuumextension 302 into the test cassette 122 beneath the test substrate 216.After installation of the test cassette 122, the fork actuator 404 canbe operated to lower the forks 406 so that the forks 406 do not contactthe test substrate 216 during operation. Operation of the fork actuator404 may be manual, or may be motorized.

FIG. 5 is a partial cutaway view of a test cassette 122 according to oneembodiment. The fork actuator 404, and the forks 406, are visible at thetop of the test cassette 122. Inside the test cassette 122 are twomandrels, a source mandrel 502 and a finish mandrel 504. The sourcemandrel 502 is rotated to dispense the test substrate 216 toward theforks 406. A first positioning roller 506 is located along a first fork406 of the fork actuator 404, and a second positioning roller 508 islocated along a second fork 406 of the fork actuator 404. Thepositioning rollers 506 and 508 position the test substrate 216 withrespect to the forks 406, as further described below. A pair oftensioners 510 are disposed on a support 512 under the secondpositioning roller 508. A tension roller 514, applies tensile force tothe test substrate 216, which is urged against the tensioners 510 by thepositioning of the second positioning roller 508 and the tension roller514, as described further below. A feed roller 516 accepts the testsubstrate 216 from the tension roller 514, and the finish mandrel 504spools the test substrate 216 after use. The test cassette 122 is mostlyenclosed by an enclosure 518, but an opening 520 in the top of theenclosure 518 provides access for the test substrate 216 to emerge fromthe enclosure and engage with the forks 406 and the vacuum extension302.

FIG. 6 is a detail view of the positioning rollers 506 and 508, with theforks 406. The test substrate 216 is shown here extending through theopening 520 in the enclosure 518. Here, the fork actuator 404 isextended to lift the test substrate 216. The test substrate 216 is thuslifted above the vacuum extension 302 so the vacuum extension 302 canextend into the test cassette 122 beneath the test substrate 216. Eachfork 406 has a flat side 602 and a round side 604 opposite the flat side602. The round side 604 contacts the test substrate 216 and provides asmooth lifting surface. The flat side 602 enables lowering the forks 406toward the positioning rollers 506 and 508 during operation withoutcontacting the positioning rollers 506 and 508.

FIG. 7 is a side view of the test cassette 122 in proximity to theprinthead housing 116 to illustrate performance of a test. The testsubstrate 216 is shown in operating configuration with the forks 406lowered. The test substrate 216 extends from the second positioningroller 508 to the tension roller 514, contacting the tensioners 510.Here, the tensioners 510 are flex springs, metal strips that areattached to the support 512 by a fastener 702 and extend away from thesupport 512 and curve back toward the support 512 forming an arch 704.The metal strip curves back toward the support 512 and contacts thesupport 512 at a landing 706 that can slide along the support 512 as thetensioner 510 flexes. As force is applied to the test substrate 216 bythe tensioning roller 514, compressive force is applied to thetensioners 510, which react by absorbing at least a portion of thecompressive force as flex. The tensioners 510 thus maintain tension onthe test substrate 216 when the vacuum is released at the vacuum surface402. The tension in the test substrate 216 maintains close proximitybetween the test substrate 216 and the vacuum surface 402 such that whenvacuum is applied at the vacuum surface 402, the test substrate 216 ischucked to the vacuum surface 402. Here, the forks 406 can be seen inretracted operating position, where the flat side 602 of the forksallows for clearance between the forks 406 and the positioning rollers506 and 508.

The printhead housing 116 includes an imaging device 708, such as acamera. The imaging device 708 is positionable over the test substrate216, over the vacuum surface 402, to capture an image of the testpattern printed on the test substrate 216. The print heads are alsolocated in the printhead housing 116, and are omitted from this view forsimplicity. The imaging device 708 is shown here with an imagingaperture that is smaller than the operating surface of the testsubstrate 216. In operation, the test module 118 and the imaging device708 are relatively moved and positioned to allow capturing a pluralityof images so that the entire test pattern can be imaged.

As can be seen in FIG. 7 , the imaging device 708 collects lightreflected from the test substrate 216 and from the vacuum surface 402.Dots printed on the test substrate 216 produce a light pattern that canbe analyzed to determine characteristics of the dots. The backgroundreflected light can be selected to maximize resolution of the dots bythe imaging device 708. For example, by choosing a color of the vacuumsurface that maximizes dot resolution, the test module can have the bestperformance. A carbon vacuum surface, as described above, will have arelatively black color, which may be best for imaging light-coloredmaterials printed on the test substrate. For imaging dark-coloredmaterials, a relatively white color vacuum surface may be useful. Suchcolor may be available by using a ceramic vacuum surface, which may beporous. In other cases, reflective surfaces, such as bare aluminum, maybe useful to provide maximum dot resolution.

FIG. 8 is a side view of the test module 118 in operating configuration.The test cassette 122 is shown coupled to the mount 120 in operatingproximity with the drive 208. The test cassette 122 has two cassetterotators 802 that extend from the test cassette 122 toward the drive 208and magnetically couple to the rotators 218 of the drive 208. Aclearance 804 is maintained between the drive rotators 218 and thecassette rotators 802. The cassette rotators 802 are coupled through theenclosure 518 to the source and finish mandrels 502 and 504. Inoperation, the drive rotators 218 are rotated, and the magnetic couplingto the cassette rotators 802 causes the cassette rotators 802 to rotate,thus rotating the source and finish mandrels 502 and 504. When a testpattern is printed on the test substrate 216, the test pattern isimaged, vacuum is discontinued at the vacuum surface 402, and then themandrels 502 and 504 are rotated to advance the test substrate 216 one“frame” or test location. A new clear portion of the test substrate 216is positioned over the vacuum surface 402, and vacuum applied to securethe test substrate 216 for another test. When the last test location ofthe test substrate 216 is used, the test cassette 122 can be removed andanother new test cassette 216 installed.

When installing and removing the test cassette 216 the tray actuator 206is operated to extend the tray 202 to the loading position. The trayactuator 206 has enough power to overcome the magnetic coupling of therotators 802 and 218 such that the test cassette 122 can be removed fromthe tray 206.

The test substrate 216 is a flexible material that can wind around themandrels and rollers. Typically, a plastic film-like material is used.The flexible material may be transparent or translucent to providesuitable contrast with the optical characteristics of the print materialdeposited on the test substrate 216 for optimal imaging.

FIG. 9A is a top view of a substrate holder 900 according to oneembodiment. The substrate holder 900 is useable with test substrates inembodiments described herein. FIG. 9B is a cross-sectional view of thesubstrate holder 900 of FIG. 9A. The substrate holder 900 can providethe vacuum surface 302 of FIG. 3 . The substrate holder 900 is a vacuumholder that flows gas through openings 902 in a surface 904 of thesubstrate holder 900. The substrate holder 900 has an internal plenum906 that supports fluid flow through the substrate holder 900 from thesurface 904 to the internal plenum 906 and out through a port 908. Avacuum source (not shown) can be fluidly coupled to the port 908 toevacuate gas between the surface 904 and a substrate disposed on or overthe surface 904 to provide secure support for the substrate. The surface904 here extends from a first end 905 of the substrate holder 900 to asecond end 907 of the substrate holder 900, opposite from the first end905. The surface 904 extends partway across the substrate holder 900. Abevel 901 connects the surface 904 to the sides 903 of the substrateholder 900, which connect the first end 905 to the second end 907.

The surface 904 has a plurality of openings 902 that provide fluid flowfrom the surface 904 to the internal plenum 906. The openings 902include a plurality of slots 910 and holes 912. The slots 910 arearranged around a periphery of the surface 904, while the holes 912 arearranged in a central area of the surface 904. The holes 912 arearranged in two rows, each row extending along a direction of a majoraxis of the substrate holder 900, the two rows on either side of themajor axis equidistant therefrom. The surface 904 has a generallyrectangular shape, with two long sides 916 and two short sides 918. Theslots 910 include a plurality of long slots 914 extending parallel tothe long sides 916 of the surface 904 and a plurality of short slots 920extending parallel to the short sides 918 of the surface 904. The slots910 generally bound a vacuum area 922 of the surface 904 where vacuumcan securely hold a substrate. The vacuum area 922 extends partway alongthe surface 904 from the first end 905 to the second end 907 of thesubstrate holder 900, and is located closer to the first end 905 than tothe second end. The long slots 914 are positioned adjacent to the longsides 916 of the surface 904. A first short slot 920 is positioned neara short side 918. A second short slot 920 is positioned opposite thefirst short slot 920, the short slots 920 and long slots 914 defining aboundary of the vacuum area 922. The surface 904 extends beyond thesecond short slot 920 to an attachment region 924 of the surface 904.The attachment region 924, located between the second short slot 920 andthe second end 907, has two holes 926 for attaching the substrate holder900 to a processing apparatus such as the test module 118. The openings902 are arranged symmetrically across the surface 904 to provide uniformfluid flow at the vacuum region 922 for a uniform attractive forcebetween the substrate and the surface 904.

The substrate holder 900 has a passage 930 for each opening 902 toprovide fluid coupling of the opening 902 to the plenum 906. Eachpassage 930 has a first section 932 having a first diameter and a secondsection 934 having a second diameter greater than the first diameter.The first section 932 of each passage 930 extends from the opening 902toward the plenum 906, while the second section 934 of each passage 930extends from the plenum 906 toward the opening 902. The first and secondsections, 932 and 934, of each passage meet at a transition 936. Here,the first section 932 of all the passages 930 are the same length andthe second section 934 of the passages 930 are the same length, but thelengths can be varied if desired to influence fluid flow patterns at thesurface 904.

Prior to attaching the substrate to the surface 904, the substratecurves above the surface 904. The larger the gap between the substrateand the surface 904, the more fluid flow is needed to attach thesubstrate to the surface 904 by vacuum. The slots 910 function as highflow openings to draw the substrate toward the surface 904 according tothe Bernoilli principle. The slots 910 draw the substrate to within anattachment zone where flow from the holes 912 can provide the finalincrement of attachment force to attach the substrate to the surface904. The symmetrical pattern of openings provides a symmetrical flowpattern to reliably position the substrate with respect to the surface904 before attachment. In this case, the slots 910 have a width that islarger than the diameter of the holes 912, which are all the same sizehere. Also, the total areal extent of the slots 910 is greater than thetotal areal extent of the holes 912, providing a larger flowcross-section through the slots 910 than through the holes 912. This hasthe effect of creating a uniform chucking force that is somewhat greaterat peripheral areas of the vacuum region 922 to attract the substratetoward the surface 904.

While the foregoing is directed to embodiments of the present invention,other and further embodiments of the present disclosure may be devisedwithout departing from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

What is claimed is:
 1. An inkjet printer, comprising: a substratesupport; a calibration module disposed adjacent to the substrate supportand comprising a stage member; and a print assembly disposed across thesubstrate support, the print assembly comprising an imaging devicepositionable to face the stage member, wherein the stage membercomprises a vacuum extension having a vacuum surface with a firstplurality of openings, including slots, at a periphery of the vacuumsurface and a second plurality of openings in a central area of thevacuum surface, wherein the total areal extent of the first plurality ofopenings is greater than the total areal extent of the second pluralityof openings.
 2. The inkjet printer of claim 1, wherein the vacuumextension comprises a porous body.
 3. The inkjet printer of claim 2,wherein the vacuum extension further comprises a holder and the porousbody is embedded in the holder.
 4. The inkjet printer of claim 3,wherein the calibration module is configured to receive a test substrateand to position the test substrate between the vacuum extension and theprint assembly.
 5. The inkjet printer of claim 4, wherein the vacuumsurface is configured to create a greater force at the periphery thereofthan at the central area thereof.
 6. An inkjet printer of claim 4,wherein the calibration module further comprises a tensioning member forengaging with the test substrate.
 7. The inkjet printer of claim 6,wherein the tensioning member is a passive tensioning member.
 8. Aninkjet printer, comprising: a substrate support; a calibration moduledisposed adjacent to the substrate support to receive a removablecassette housing a test substrate, the calibration module comprising astage member; and a print assembly disposed across the substratesupport, the print assembly comprising a printhead and an imaging devicepositionable to face the stage member, wherein the stage membercomprises a vacuum extension with a porous body that has a vacuumsurface with a plurality of high flow openings at a periphery thereoffor providing a greater force at the periphery of the vacuum surfacethan at a central area of the vacuum surface.
 9. The inkjet printer ofclaim 8, wherein the vacuum extension further comprises a holder, andthe porous body is embedded in the holder.
 10. The inkjet printer ofclaim 9, wherein the imaging device and the printhead are independentlymovable.
 11. The inkjet printer of claim 10, wherein the calibrationmodule further comprises a tensioning member for engaging with the testsubstrate.
 12. The inkjet printer of claim 11, wherein the tensioningmember is a passive tensioning member.
 13. An inkjet printer,comprising: a substrate support; a calibration module disposed adjacentto the substrate support and comprising a linear positioner and a stagemember that has a vacuum extension having a vacuum surface with aplurality of openings configured to provide a greater chucking force atthe periphery of the vacuum surface than at a central area of the vacuumsurface; and a print assembly disposed across the substrate support, theprint assembly comprising a printhead and an imaging device positionableto face the stage member, wherein the printhead and the imaging deviceare independently movable.
 14. The inkjet printer of claim 13, whereinthe vacuum surface comprises a porous body that is ceramic.
 15. Theinkjet printer of claim 13, wherein the vacuum extension comprises aporous body disposed in a holder.
 16. The inkjet printer of claim 13,wherein the calibration module is configured to receive a removable testsubstrate assembly containing a test substrate.
 17. The inkjet printerof claim 16, wherein the calibration module further comprises aplurality of flex springs for maintaining a tension of the testsubstrate.